| Heavy metals and their compounds are widely used in different industrial applications. Increase in their usage has resulted in an increase in the environmental pollution. Heavy metals are also one of the most widespread causes of pollution both in water and in the soil, and they are non-degradable and therefore continue to accumulate in water bodies. Because of their toxic properties and the tendency for bio-accumulation in the food chain, it is imperative to take effective precautions and to reduce the concentration levels of heavy metals in waters. In recent year, the presence of increasing levels of these metals in the environment is causing serious concern in public opinion owing to the toxicity shown by most of them. The pyrite widely exists in the nature, and it has good stability and reducibility. The purpose of this study is to explore the characteristics of milled pyrite and its application in the field of heavy metal removal and environmental remediation.This study conducted a large number of experiments to investigate the special properties of milled pyrite when it is used in removing heavy metal.Firstly, nano pyrite was prepared by ball milling, the characterization results showed that the main component of the pyrite was FeS2;Secondly, the influences of different reaction conditions, which include the using dosage of pyrite, initial p H, reaction time and temperature were studied using batch experiments. The results showed that:.(1) The removal efficiency of milled pyrite is higher than natural pyrite efficiency.(2) The removal efficiency of Cr6+,Cd2+ and Pb2+ increased with the increase of the using dosage of pyrite and milling time. When these values increaed to some extent, the removal efficiency didnot increase anymore.(3) The removal efficiency of Cd2+ and Pb2+ increased with the increase of pH values. But the removal efficiency of Cr6+ decreased with the increase of pH values.(4) The removal efficiency was also influenced by the reaction temperature. With the increase of temperature in the range of 25℃ to 45℃, the removal efficiency increased.(5) Through the desorption experiment, it can be concluded that the adsorption between milled pyrite and heavy metal is stable, and heavy metal is not easy to be desorption.(6) By comparison the pyrite and iron-manganese ore, we can conclude that the pyrite can not only absorb heavy metal but also react with heavy metal by redox reaction.(7) The reaction mechanism of nano pyrite and Cr6+, Cd2+ and Pb2+ was investigated. The results showed that the pyrite reacted with Cr6+ mainly by redox reaction and reacted with Cd2+ and Pb2+ mainly by adsorption and precipitation.(8) The dynamic adsorption data of Cr6+, Cd2+ and Pb2+ on nano-sized pyrite were well described by pseudo second-order kinetic equation.This study provided a method which using milled pyrite to remove Cr6+, Cd2+ and Pb2+. The best reaction conditions were determined by analysing the experiment results, and these reaction mechanisms can be used to guide the experiments in the future. |
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